Kyverna plans to submit mivocabtagene autoleucel to the FDA for approval in the first half of 2026. If approved, it would be the first CAR T therapy for an autoimmune disease.
Kyverna Therapeutics’ investigational CAR T therapy mivocabtagene autoleucel significantly improved mobility in a pivotal study of stiff person syndrome, paving the way for its regulatory filing next year.
The mid-stage performance of mivocabtagene autoleucel (miv-cel) was “impressive,” according to analysts at William Blair, writing in a Monday note to investors, adding that the data are “extremely positive and supportive of the upcoming BLA submission for miv-cel in SPS, setting it up to potentially be the first FDA-approved CAR-T for the treatment of an autoimmune disease.”
Kyverna was up 23% at market close on Monday, trading at $10.82 per share.
In a news release on Monday, the company reported that patients on miv-cel saw a 46% median improvement at 16 weeks on the timed 25-foot walk (T25FW), a key measure of mobility. This effect was statistically significant. That “exceeded our expectations,” William Blair said.
Additionally, 81% of patients achieved at least a 20% improvement on the T25FW.
Miv-cel also aced all secondary endpoints, including ambulation, sensitivity, disability and distribution of stiffness across the body. At the time of readout, all patients were off immunotherapies and none needed rescue therapy—a fact Kyverna said highlights “miv-cel’s potential to provide unprecedented clinical benefit while significantly reducing or eliminating chronic treatment burden.”
As for safety, the biotech reported no high-grade cases of cytokine release syndrome or immune effector cell-associated neurotoxicity syndrome. Instances of grade 3/4 neutropenia, a known side effect of CAR T, were manageable.
With these data in hand, Kyverna expects to file its biologics license application for miv-cel in stiff person syndrome in the first half of 2026.
With fewer than 5,000 affected patients in the U.S., stiff person syndrome is a rare neurologic disorder that arises when a person’s antibodies attack certain cells in the brain and central nervous system. The result is the progressive and erratic stiffening of muscles and painful spasms that define the disease. Other symptoms include pain, difficulty walking and disruptions in daily activities.
Miv-cel is a CAR T therapy that targets the CD19 protein found on B cells, as well as the stimulatory protein CD28 on T cells. Through this mechanism, miv-cell depletes autoimmune B cells and helps reset the immune system.
Aside from stiff person syndrome, Kyverna is also developing miv-cel for generalized myasthenia gravis, for which the asset in October demonstrated a 100% response rate in a Phase III study—findings that William Blair said at the time establish “a new efficacy standard in the field.” The biotech is also looking at the potential of miv-cel in other immune disorders, including multiple sclerosis and rheumatoid arthritis.
